• Composites Research
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• v.12 no.5
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• pp.80-86
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• 1999

Mechanical characteristics of composite laminates and cylindrical shell using scrim of glass scrim are evaluated in this paper. Composite laminates and cylindrical shells are made by inserting carbon scrim or glass scrim between layers. The mechanical properties are routinely characterized by ASTM stands. Experimental results show that the mechanical properties of UD prepreg in the transverse direction are highly improved by inderting scrims between layers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1590-1596
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• 2001

The shot peening process is most often used to improve fatigue properties of metal parts. The single most critical parameter of the shot peening process is the shot ball itself. Without the correct quality media, all other shut peening parameters are extraneous and the desired fatigue improvement and consistency of improvement will not be achieved. Shot peening involves modifications of the surface and subsurface condition of a material that can be described by the change of the residual stresses, the hardness, and the surface roughness. This Paper Presents the shot peening to optimize the shot ball parameters. The effect of shot peening parameter on the surface roughness, surface hardness and residual stress are investigated.

• Proceedings of the KAIS Fall Conference
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• 2009.05a
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• pp.368-371
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• 2009

선박용 침몰방지용 부양백의 소재를 개발하는데 있어 부양백 내의 부양기체인 질소가스가 장기 유지특성 보유 소재(gas barrier properties), 코팅 경량 직물형태로서 경량성 보유 소재 기술, 장수명의 부양 백 소재 개발, Silicone/Nylon/Silicone 코팅 다층 구조의 고강도 유지 특성 유지 및 재활용성 특성 유지 부양백 소재를 개발하였다. 이들 소재를 개발하는데 있어 Nylon 직물별 물성 조사로 우리가 개발 목표로 하는 nylon의 denier 별로 구매하여 이들에 대한 기본물성인 인장특성, 내노화성, 기체투과도 및 복원성을 조사하였으며, Nylon 직물에 Silicone의 코팅시험을 실시하였고, 최적 코팅 silicone의 선정을 통해 최적의 균일한 두께 특성, 최적의 강도 유지특성 및 gas barrier 특성을 갖는 silicone 및 코팅두께를 선정하여 최종적으로 부양백용 gas barrier성 수지의 선정하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.159-163
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• 2011

천수방정식에 대한 Lax-Wendroff 기법을 기반으로 한 유한요소 모형을 낙동강 상류부 단호교 지역에 적용하였다. 모형의 검증을 위하여 이동경계에 대한 Thacker (1981)의 정확해와 젖음-마름 기법(wet-dry scheme)을 이용한 본 모형의 수치해를 비교하여 대체로 잘 일치함을 알게 되었다. 또한, U자형 만곡부를 포함한 수로의 흐름에 적용하여, 기존의 수리실험 결과, 수치모의 결과와 비교하고, 모형의 적용 가능성을 확인하였다. 낙동강 상류지역에 위치한 단호교지역에 본 모형을 적용하고, 이를 기존 유한차분법에 의한 수치해와 비교하였다.

• Water for future
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• v.28 no.1
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• pp.57-70
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• 1995

A water quality model RIV-LAGI for the toxic pollutant transport analysis is developed based on varied flow analysis and one-dimensional Lagrangian method. Applying to the prismatic channel, it shows accurate results compared with the analytical solutions. The model is applied to the Nakdong River to analyze the phenol spill accident, which occurred on March, 1991. The computed results have good agreements with the observed data. The travel times in the reach of Gumi to Mulkeum based on the monthly average and minimum flow are computed. The suggested model can be used to study the impact of the chemical spills and clean-up plans in the Nakdong River.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.77-84
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• 2006

Unlike homogeneous material structure, the behavior of masonry structure is not perfectly elastic even in the range of small deformations because it is a non-homogeneous and anisotropic composite structural material, consisting of masonry units, mortar, and grout. This paper proposes a simplified way of investigating the evolution of the deformation and damage of the structure subjected to a series of successive ground motions with varying shaking. Especially, the most simple but useful algorithm of Fast Fourier Transformation (FFT) has been adopted to investigate the evolution of the deformation and damage of the structure tested on the shaking table. Moreover, the development of a hi-linear curve for an equivalent SDOF system which is obtained by exploiting the frequency and stiffness relationship was discussed. Finally, some important findings related to inelastic properties of the URM are summarized.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.63-68
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• 2003

Shot peening process is most often used to improve the fatigue properties of metal parts, In order to achieve an optimum, repeatable, and reliable fatigue enhancement from the shot peening process, the important shot peening parameters must be optimized, In this paper, the optimum peening intensity(Almen intensity) condition is investigated by experiment. Rotary bending fatigue test has been adopted to investigate the effects of optimum peening on the fatigue characteristics, Experimental results show that the fatigue strength and fatigue life has been tremendously increased by optimum-peening treatment. However, the fatigue strength and fatigue life has been decreased by under or over peening.

• Composites Research
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• v.36 no.3
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• pp.180-185
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• 2023

This paper investigates the impact of fiber dispersion on the internal structure and mechanical strength of SiC_f/SiC composites manufactured using spread SiC fibers. The fiber volume ratio of the specimen to which spread SiC fiber was applied decreased by 9%p compared to the non-spread specimen, and the resin slurry impregnated between the fibers more smoothly, resulting in minimal matrix porosity. In order to compare the fiber dispersion of each specimen, a method was proposed to quantify and evaluate the separation distance between fibers in composite materials. The results showed that the distance between fibers in the spread specimen increased by 2.23 ㎛ compared to the non-spread specimen, with a significant 42.6% increase in the distance between fiber surfaces. Furthermore, the 3pt bending test demonstrated a 49.3% higher flexural strength in the spread specimen, accompanied by a more uniform deviation in test data. These findings highlight the significant influence of SiC fiber dispersion on achieving uniform densification of the SiC_f/SiC matrix and increasing mechanical strength.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.761-766
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• 2006

Polymer composite are increasingly considered as structural components for use in civil engineering, on account of their enhanced strength-to-weight ratios. Unsaturated polyester (UP) resin have been widely used for the matrix of composites such as FRP and polymer composite, due to its excellent adhesive. Polymer nanocomposites are new class of composites derived from the nano scale inorganic particles with dimensions typically in the range of 1 to 1000 nm that are dispersed in the polymer matrix homogeneously. Owing to the high aspect ratio of the fillers, mechanical, thermal, flame, retardant and barrier properties are enhanced without significant loss of clarity, toughness or impact strength. To prepare the MMT (Montmorillonite)-UP exfoliated nanocomposites, UP was mixed with MMT at $60^{\circ}C$ for 3 hours by using pan mixer. XRD (X-ray diffraction) pattern of the composites and TEM (Transmission Electron Micrographs) showed that the interlayer spacing of the modified MMT were exfoliated in polymer matrix. The mechanical properties also supported these findings, since in general, tensile strength, modulus with modified MMT were higher than those of the composites with unmodified MMT. The thermal stability of MMT-UP nanocomposite is better than that of pure UP, and its glass transition temperature is higher than that of pure UP. The polymer concrete made with MMT-UP nanocomposite has better mechanical properties than of pure UP. Therefore, it is suggested that strength and elastic modulus of polymer concrete was found to be positively tensile strength and tensile modulus of the MMT-UP nanocomposites.

• Journal of Dairy Science and Biotechnology
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• v.33 no.3
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• pp.203-207
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• 2015

The majority of food drying processes are based on the use of thermal energy. However, such methods may deteriorate the quality of the final product. Freeze-drying is one of the most useful processes for drying thermosensitive substances. Food that contains beneficial bacteria, for example, is susceptible to heat treatment, but during freeze-drying beneficial bacteria are preserved in these food items. The primary goals of this study were to develop yogurt snacks and to compare the viability of lactic acid bacteria (LAB) in yogurt snacks under different freeze-drying temperatures. In addition, the survival of LAB during storage was investigated. Survival of LAB in freeze-dried yogurt snacks gradually decreased over 16 weeks of storage. LAB had a residual viability of 25.5% after 16 weeks of storage at room temperature. LAB survived better in freeze-dried plain yogurt snacks than in freeze-dried strawberry yogurt snacks during storage. Freeze-dried yogurt snacks contained 11.9% fat, 57.1% carbohydrate, and 18.7% protein. In conclusion, the viability of LAB in freeze-dried yogurt snacks depends on the temperature during freeze-drying: the higher the freeze-drying temperature, the lower the viability of LAB in yogurt snacks. The viability of LAB in yogurt snacks was also dependent on the moisture content and nutritional value.